How Does a Magnetic Flowmeter Work?

This meter has no part that spins in the flow. It works by Faraday's law: liquid moving through a magnetic field makes a small voltage, so the liquid needs a minimum conductivity, typically about 5 microsiemens per centimeter (µS/cm); wastewater is usually far above that. The pipe usually must remain full for a good reading. Air pockets, bad grounding, coating, or wiring trouble can affect performance.

A pump is running, but a meter in a partly full high point reads poorly. The operator checks the piping condition and meter diagnostics before changing the process.

A magnetic meter depends on contact between the liquid and its measuring area. An empty pipe or large air pocket can create a zero, unstable, or full-scale reading. Coating on the electrodes may cause slow drift. Electrical grounding and bonding are also part of the installation. Operators should not open wiring compartments unless qualified. They can still check whether pumps are running, the pipe should be full, valves are open, and the displayed total changes in a sensible way.

Confirm the pipe should be full before treating a low reading as real.

Key point: A magnetic flowmeter needs conductive liquid in a full pipe. An empty pipe or air pocket can give a zero, unstable, or full-scale reading.